The invention relates generally to apparatus for cleaning the interior surface of the wall of a process vessel and, more particularly, to apparatus for removing scale and other deposits from the interior surface of the wall of digester vessels such as those used in an aluminum production process.
Typically, vessels of this type are large cylindrical vessels having a diameter of approximately 9 to 14 feet and a height on the order of 50 to 75 feet. A hard glass-like scale gradually builds up on the interior surface of the wall of the vessel as the process is continuously practiced therein. The thickness of the scale can be on the order of 5 to 6 inches and removal thereof is extremely labor intensive, dangerous and time consuming due to the configuration of the vessel and the limitations imposed by manually operated tools and by known scaffolding and rigging arrangements within the vessel. One example of an apparatus for chipping the scale from the inside of a vessel is disclosed in U.S. Pat. No. 5,020,183 which is owned by the assignee of the instant application. The limited access to the interior of a typical aluminum process digester vessel also presents a problem because the restricted opening afforded by the manhole at the closed top of the vessel is usually only 19 to 32 inches in diameter which prevents the use of any but lightweight tools and rigging of limited dimensions.
The present invention solves many of the problems heretofore encountered in cleaning the inner surface of the wall of an aluminum digester or other process vessel. The present invention provides apparatus which substantially reduces the amount of time and expense required to clean the interior surface of the wall of a vessel while concurrently producing a relatively clean scale-free wall surface. Additionally, the utilization of this equipment creates a safe working environment since the operator is not located inside of the vessel.
The present apparatus includes a rigging for lowering a chipping hammer into the vessel and for positioning that chipping hammer so that the bit can contact the full interior surface of the vessel wall both radially and vertically. The hammer is a heavy duty impact tool which has high power capabilities and can remove the very thick and hard deposits which are extremely difficult and time consuming when manual tools are used.
Still further, the apparatus of the invention provides a stable construction having a plurality of hydraulically operated stabilizer arms within the vessel to contact the interior surface of the vessel wall. The equipment can be collapsed into a configuration which can be lowered through the relatively restricted access manhole at the upper end of the vessel and can be placed in its operating condition after it is inside the vessel.
An electronic camera is attached to the boom of the impact tool so that the operator is in constant visual contact with the operation of the impact tool chipping bit to monitor the operation.